Improved differential evolution based PA energy efficiency optimization scheme with joint polarization-QAM in OFDM systems

To optimize the energy efficiency of non-linear power amplifier (PA) in orthogonal frequency division multiplexing (OFDM) systems, an energy efficiency optimization scheme based on improved differential evolution algorithm is proposed. The scheme utilizes joint polarization-QAM to promote energy efficiency by taking the advantages of both QAM and polarization modulation in the linear and nonlinear areas of PA, respectively. However, the energy efficiency is effected by the changes of the factors such as modulation orders, PA characteristics, channel of polarization mode dispersion, channel compensation matrix and symbol error rate (SER) and data rate requirements. In addition, they can also interact with each other. To optimize energy efficiency, the energy efficiency maximization problem regarding these factors is formulated, and an improved algorithm based on differential evolution is proposed to obtain competitive performance when solving the problem. Therefore, the energy efficiency optimization scheme in this paper enables not only adaptation of modulation as adaptive polarization-QAM scheme, but also joint adjustment of PA characteristics and channel compensation matrix to achieve higher energy efficiency. The simulation results under the same SER threshold show that the energy efficiency of proposed energy efficiency optimization scheme based on improved differential evolution with joint polarization-QAM can be improved by up to 43% compared with adaptive polarization-QAM scheme in OFDM systems.